AJ Nilles doesn’t have one of the high-visibility positions in the San Diego Symphony. He’s a new section violist, joining the orchestra fresh out of the Juilliard School of Music.

But within the first few days of rehearsals after Nilles joined the orchestra earlier this year, just about everybody in the 80-member ensemble had made a point of introducing themselves.

“I’d heard that this orchestra is much friendlier than most,” said Nilles, during a Summer Pops rehearsal break. “For me personally, to be fresh into the professional world and be surrounded by people who are friendly and nurturing has been a nice, warm experience.

“And, of course, it’s a great orchestra. It’s really on its way up, which is refreshing.

Over the past year, the orchestra had added five new musicians, most of them younger: Nilles; section violinist Anna Skálová; principal flutist Rose Lombardo; highly experienced third trumpet Ray Nowak; and section violinist Yeh Shen, formerly a member of the Houston Symphony.

“I’m happy to be here,” said Shen, who will be onstage with the orchestra when it opens its 102nd season Friday through Sunday at Copley Symphony Hall. “The orchestra has improved a lot. It’s a young orchestra with a lot of potential.”

About half of the symphony’s 80 musicians were hired since Jahja Ling became music director in 2003, and many of them are relatively young. That has little to do with Ling’s personal preferences. The auditions for every opening, which often attract hundreds of applicants, are blind, performed behind a screen. The screen is removed for the finalists, with the winner chosen by Ling and a committee from the orchestra.

“You have to have all the basic things — intonation, rhythm, dynamics …” Ling said. “But beyond that, there has to be something that speaks to the heart — a phrase, something that when he or she plays it, can the audience feel it? Can the audience be moved by it? Can he move me? Can he move the committee members?”

It can be difficult for musicians to control their own destiny, not only because of the sometimes unpredictable preferences of some audition committees but because only certain orchestras even have openings.

“As a musician, you can’t really pick,” Lombardo said. “You go where the openings are, so we all feel really lucky we get to be here.”

As principal flute, Lombardo has a unique leadership position. She takes her place in an expert woodwind section that includes principal oboe Sarah Skuster, who joined the orchestra in 2009, and principal clarinet Sheryl Renk and principal bassoon Valentin Martchev, who have been with the ensemble considerably longer (Renk since 1991).

“What’s great is I don’t really feel that the people who have been here for a while, like they are just kind of sitting back,” Lombardo said. “People have been helping me out, showing me the ways of the world since I’ve joined the orchestra.

“I’m sure they played these things 100 million more times than me, but they are still at it, still fresh, which is really inspiring for someone my age to see.”

For Nowak, whose résumé includes ensembles in Spain, Mexico and Japan, he’s delighted at the orchestra’s vitality and isn’t taking anything for granted.

“Everyone knows a lot of orchestras are having problems,” he said. “Times are tough. People elsewhere are either taking pay cuts or their positions are cut, or they are forced out because they can’t make ends meet.

“I think musicians, myself included, are taking it a lot more seriously now. Maybe it was taken for granted 20 years ago (that you could get a good job and stay there); you see a lot less of that now. This orchestra is young, but whether someone is young or old, you see that fire inside, the excitement. I love seeing that. I love being a part of it.”